LAUSR

Purpose To evaluate the combination of 90 Y radioembolization (Y90) and drug-eluting bead irinotecan (DEBIRI) microspheres in the VX2 rabbit model. Materials and Methods An initial dose finding study was performed in 6 White New Zealand rabbits to identify a therapeutic but subcurative dose of Y90. In total, 29 rabbits were used in four groups: Y90 treatment ( n  = 8), DEBIRI treatment ( n  = 6), Y90 + DEBIRI treatment ( n  = 7), and an untreated control group ( n  = 8). Hepatic toxicity was evaluated at baseline, 24 h, 72 h, 1 week, and 2 weeks. MRI tumor volume (TV) and enhancing tumor volume were assessed baseline and 2 weeks. Tumor area and necrosis were evaluated on H&E for pathology. Results Infused activities of 84.0–94.4 MBq (corresponding to 55.1–72.7 Gy) were selected based on the initial dose finding study. Infusion of DEBIRI after Y90 was technically feasible in all cases (7/7). Overall, 21/29 animals survived to 2 weeks, and the remaining animals had extrahepatic disease on necropsy. Liver transaminases were elevated with Y90, DEBIRI, and Y90 + DEBIRI compared to control at 24 h, 72 h, and 1 week post-treatment and returned to baseline by 2 weeks. By TV, Y90 + DEBIRI was the only treatment to show statistically significant reduction at 2 weeks compared to the control group ( p  = 0.012). The change in tumor volume (week 2—baseline) for both Y90 + DEBIRI versus control ( p  = 0.002) and Y90 versus control ( p  = 0.014) was significantly decreased. There were no statistically significant differences among groups on pathology. Conclusion Intra-arterial Y90 + DEBIRI was safe and demonstrated enhanced antitumor activity in rabbit VX2 tumors. This combined approach warrants further investigation.